Fuel efficiency of an engine may be improved by temporarily deactivating selected cylinders of the engine. The engine cylinders may be deactivated by stopping fuel flow and spark to the engine cylinders. Once a portion of the engine cylinders are deactivated, the engine's active cylinders may provide an equivalent amount of torque as compared to when all cylinders are operating, and the active cylinders may operate at a higher volumetric efficiency. Further, the engine may operate with less pumping losses when a portion of engine cylinders are deactivated. However, residual fuel and oil in a deactivated cylinder may accumulate on the cylinder's spark plug such that the spark plug fouls and may not provide a desirable spark when an attempt is made to reactivate the cylinder. Consequently, engine emissions and torque production may degrade.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for providing spark to an engine, comprising: operating a first group of cylinders and deactivating a second group of cylinders, the second group of cylinders deactivated via stopping spark and fuel flow to the second group of cylinders; and providing spark without providing fuel to a cylinder of the second group of cylinders a predetermined duration after the second group of cylinders is deactivated.
The possibility of spark plug fouling for spark plugs of deactivated cylinders may be decreased by periodically reactivating spark in the cylinder without resuming fuel flow to the deactivated cylinder. Further, in some examples, the amount of energy supplied to the spark plug when the cylinder is deactivated may be increased compared to an amount of energy supplied to the spark plug when the engine is operated at the same speed and load with all cylinders activated. The additional energy may help to remove hydrocarbons and/or carbonaceous soot that may form on a spark plug. In this way, it may be possible to reduce the possibility of fouling spark plugs in cylinders that have been deactivated.
The present description may provide several advantages. For example, the approach may reduce the possibility of spark plug fouling in deactivated cylinders. Further, portions of the approach may be applied in response to a request to deactivate cylinders so that the cylinders may be deactivated for a longer period of time before energy is supplied to spark plugs in a cylinder that is not combusting an air-fuel mixture. Thus, the approach may preemptively address potential spark plug fouling for deactivated cylinders.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.